A 75-year-old man presented to the gastroenterology department with a 4-week history of severe watery diarrhea (at least 20 times a day) and appetite loss. He had been taking amlodipine 5 mg once daily for 12 years and olmesartan 20 mg once daily for 11 years because of hypertension. His vital signs were stable, and the abdominal examination was normal. He was neither anemic nor icteric. His body weight decreased by 5 kg during the last 1 month. Laboratory evaluation showed that serum creatinine level and serum uric acid level were elevated at 1.46 mg/dL (range 0.6–1.1) and 12.1 mg/dL (range 3.6–7.0), respectively.